New research suggests that a father’s diet before conception may influence his baby’s body composition. Scientists in Brazil report that higher consumption of ultra-processed foods by fathers was associated with subtle but measurable differences in fat distribution in newborns.
Ultra-processed foods are industrially manufactured products that are typically high in sugar, unhealthy fats, salt and food additives while providing relatively few essential nutrients. Previous research has linked frequent consumption of these foods to higher risks of cardiovascular disease, cancer and neurodegenerative disorders in adults.
The findings, published in Nutrition Research, shift greater attention toward the father’s role in preconception health. Until now, most medical recommendations have focused primarily on maternal nutrition before and during pregnancy, while paternal diet has received much less attention.
How the study was conducted
Researchers from the University of São Paulo followed 43 family triads consisting of a mother, a father and their newborn infant. Pregnant women were recruited first, and their partners joined the study afterward.
Both parents completed two detailed 24-hour dietary recalls, describing everything they had eaten and drunk during the previous day. Researchers then calculated the percentage of each participant’s total daily energy intake that came from ultra-processed foods.
After delivery, the infants underwent detailed physical assessments. Researchers measured birth weight, length, body circumferences, skin-fold thickness at multiple locations and overall body composition.
These measurements allowed the team to evaluate not only the babies’ size but also how body fat was distributed.
Babies showed differences in fat distribution
The analysis found that fathers who consumed larger amounts of ultra-processed foods tended to have babies with higher birth weight and greater weight relative to their length.
Their newborns also showed thicker skin-fold measurements around the thighs and hips, suggesting greater fat accumulation in these specific regions.
Interestingly, researchers did not observe a significant increase in total body fat. Instead, the differences appeared to involve where fat was stored rather than the overall amount of fat.
On average, ultra-processed foods accounted for approximately 30 percent of fathers’ daily calorie intake.
Commonly consumed products included processed meats, sugar-sweetened beverages, cookies and other packaged snack foods.
Possible biological mechanisms
Because the study was observational, it cannot prove that fathers’ diets directly caused these differences in newborn body composition.
However, the findings fit within a growing body of evidence suggesting that paternal health before conception may influence fetal development through epigenetic mechanisms.
Researchers believe poor nutrition may alter sperm quality and modify epigenetic markers such as DNA methylation, which regulate how genes are switched on and off. These changes could potentially influence a child’s future susceptibility to obesity, insulin resistance and other metabolic disorders.
Ultra-processed foods are also known to promote chronic inflammation and oxidative stress through increased production of reactive oxygen species.
This inflammatory environment may impair sperm quality, motility and DNA integrity, potentially altering the biological signals transmitted to the embryo during conception.
One possible mechanism involves the paternal IGF-II gene, which produces a protein essential for fetal growth. Previous studies suggest that diets rich in processed foods may alter epigenetic regulation of IGF-II in sperm, potentially influencing how this gene functions during embryonic development.
Why fathers’ nutrition deserves more attention
Preconception counseling has traditionally focused on women by emphasizing folic acid supplementation, healthy body weight and avoiding alcohol or smoking.
The new findings suggest fathers should also be included in conversations about healthy lifestyle habits before pregnancy.
Although larger studies are needed to confirm these observations and clarify the biological mechanisms involved, researchers say the practical message is already straightforward.
Reducing ultra-processed foods while increasing consumption of minimally processed foods such as fruit, vegetables, whole grains and lean protein sources may benefit not only men’s own health but also the health of future children.
The Brazilian researchers recommend larger long-term studies to determine whether the observed differences in birth weight and fat distribution persist into childhood or increase the risk of obesity, diabetes and other metabolic diseases later in life.
As evidence continues to grow that sperm can carry biological signatures of a man’s diet and lifestyle, researchers argue that preparing for pregnancy should increasingly be viewed as a shared responsibility rather than one focused almost exclusively on maternal health.
